1. Field of the Invention
This invention relates to automobile suspensions.
2. Brief Description of the Prior Art
A prior art suspension of strut type as shown in FIG. 1, has a lower arm 1 having an inner end 2 fulcrumed to the vehicle body and a strut unit 3 having a piston rod upper end 4 also coupled to the vehicle body. The lower end of the strut is rigidly coupled to a wheel carrier 5, which is in turn coupled to the outer end of the lower arm 1. Vertical motion of the strut 3, which is restricted by an arcuate motion of the lower arm 1 ABOUT the the automobile body side coupling points 2 and 4, is coupled to the wheel carrier 5 to cause a fixed vertical motion thereof. In a prior art suspension of double wishbone type as shown in FIG. 2, an upper and a lower arm 6, 7 have their inner ends both coupled to the automobile body and their outer ends both coupled to wheel carrier 8, these arms undergoing arcuate motions about their automobile body side coupling points as support points cause a fixed vertical motion of the wheel carrier 8.
In the prior art suspensions, the geometry in the vertical motion of the wheel carrier is determined by the length, mounting position, mounting angle, etc. of the upper and lower arms having predetermined lengths, with respect to the automobile body side coupling points of these arms as support points.
Thus, in the suspension, usually of the strut type, the wheel carrier 5 undergoes revolution about point O of intersection between a right angle line extending from the strut piston upper end 4 toward the automobile body and the axis of the lower arm 1. However, on the bump side the distance between the center O of revolution noted above and the tire center P in contact with the ground, i.e., 2 the "swing arm length", is increased with bumping. This means that the negative tire camber change is small. In addition, on the rebound side the positive camber change is increased. Further, the tread changes with respect to both the bump and rebound are large. Therefore, the time performance can not be sufficiently utilized, which is undesired for the improvement of the revolution performance. Besides, on unlevel road surfaces the vehicle body rocks to the left and right, thus resulting in unstable straight running.
The double wishbone type suspension is superior to the strut type one in that it permits optimmization of the suspension geometry and provides high freedom of design. However, if sufficient lengths of the upper and lower arms 6 and 7 can not be secured due to insufficient available space, it leads to insufficient vertical stroke of tire, sudden excessive camber and tread changes, unnatural movement in the transversal direction, reduced convergence period and consequent lack of steadiness of motion.